Re: some ?? re failed disk and resyncing of array

whollygoat@letterboxes.org wrote:

On a boot a couple of days ago, mdadm failed a disk and
started resyncing to spare (raid5, 6 drives, 5 active, 1
spare).  smartctl -H <disk> returned info (can't remember
the exact text) that made me suspect the drive was
fine, but the data connection was bad.  Sure enough the
data cable was damaged.  Replaced the cable and smartctl
sees the disk just fine and reports no errors.

- I'd like to readd the drive as a spare.  Is it enough
to "mdadm --add /dev/hdk" or do I need to prep the drive to
remove any data that said where it previously belonged
in the array?

That should work.
Any issues and you can zero the superblock (man mdadm)
No need to zero the disk.

- When I tried to list some files on one of the filesystems
on the array (the fact that it took so long to react to
the ls is how I discovered the box was in the middle of
rebuiling to spare)

This is OK - resync involves a lot of IO and can slow things down. This is tuneable.

it couldn't find the file (or many 
others).  I thought that resyncing was supposed to be
transparent, yet parts of the fs seemed to be missing.
Everything was there afterwards.  Is that normal?

No. This is nothing to do with normal md resyncing and certainly not expected.

- On a subsequent boot I had to run e2fsck on the three
filesystems housed on the array.  Many stray blocks, 
illegal inodes, etc were found.  An artifact of the rebuild
or unrelated?

Well, you had a fault in your IO system there's a good chance your O broke.

Verify against a backup.

David


-- 
"Don't worry, you'll be fine; I saw it work in a cartoon once..."